Jesus speaking in Parables.
Matt 8:10-13: - 10 When Jesus heard it, He marveled, and said to those who followed, "
Assuredly, I say to you, I have not found such great faith, not even in Israel! 11 And I say to you that many will come from east and west, and sit down with Abraham, Isaac, and Jacob in the kingdom of heaven. 12 But the sons of the kingdom will be cast out into outer darkness. There will be weeping and gnashing of teeth." 13 Then Jesus said to the centurion, "
Go your way; and as you have believed, so let it be done for you." And his servant was healed that same hour.
NKJV
Matt 22:11-13: - 11 "
But when the king came in to see the guests, he saw a man there who did not have on a wedding garment. 12 So he said to him, 'Friend, how did you come in here without a wedding garment?' And he was speechless. 13 Then the king said to the servants, 'Bind him hand and foot, take him away, and cast him into outer darkness; there will be weeping and gnashing of teeth.'
Matt 25:29-30: - 29 '
For to everyone who has, more will be given, and he will have abundance; but from him who does not have, even what he has will be taken away. 30 And cast the unprofitable servant into the outer darkness. There will be weeping and gnashing of teeth.'
NKJV
These re the three references to the "Outer Darkness."
In the first passage Jesus was about the Israelites as being the Sons of "God's Kingdom" and that they because of their unbelief will be cast into the Outer Darkness.
In the second passage, God commands that the man without the wedding Garment be thrown into the outer darkness. The man was not able to discern the difference between him and the other guests at the wedding feast. He was not cloaked with a wedding garment because of his lack of a meaningful relationship with God.
In the third passage, Jesus was describing, in a parable, how Satan goes away to be locked up in the Bottomless pit for a long period of time, and when Satan returned, he approached his three servants, two of which had advanced Satan's influence over the peoples of the earth while the third servant who was also righteous was deemed by Satan to be a wicked servant because he refused to oppress his fellow neighbours living around him and as such he did not use the talent he was given to bring oppression upon the peoples of the earth around him. He challenged Satan that he had no right to the harvest as he had not prepared the field, sown the seed or watered and tended the wheat as it grew, to which Satan readily agreed with his "wicked servant," and commanded his other servants to cast the "wicked servant" into the outer darkness where there will be weeping and gnashing of teeth. By this act Satan was trying to act like God. By excluding his Wicked Servant from his presence, Satan is hoping that the light that the Wicked Servant shone upon Satan's dominion will not be seen because in Satan's opinion he has banished God's Light to the outer darkness with respect to his light.
The Outer Darkness is where God's light is not allowed to shine.
Shalom
The outer darkness is where God's light is completely absorbed by Satan's darkness.
Satan in trying to emulate God is attempting to claim that He is the light in this world, denying that this is God's possession and not his.
Those who inhabit the darkness will be judged to be unrighteous